Hydraulic friction draft gear



3, 1965 H. w. MULCAHY ETAL 3,198,346

HYDRAULIC FRICTION DRAFT GEAR 5 Sheets-Sheet 1 Filed 061;. 9, 1963 INVENTQR. Harry W Mu/ca/v Jo/ 7. E// s, I. W

3, 1965 H. w. MULCAHY ETAL 3,198,346

HYDRAULIC FRICTION DRAFT GEAR 3 Sheets-Sheet 2 Filed Oct. 9, 1963 1965 H. w. MULCAHY ETAL 3,198,346

HYDRAULIC FRICTION DRAFT GEAR Filed Oct. 9, 1963 5 Sheets-Sheet 5 United States Patent 3,198,346 HYDRAULIC FRECTEQN DRAFT GEAR Harry W. Mulcahy, (Jhicago Hei hts, and ,fohn T. Ellis, Jan, Sholrie, Ili.. assignors to W. H. Miner, fun, (Ihicago, Iil., a corporation of Delaware Filed Oct. 9, 1963, der. No. 314,993 6 Claims. (Cl. 213-43) This invention relates in general to shock absorbing mechanisms for railway cars and, more particularly, to draft gears having both friction and hydraulic shock absorbing components.

Most combination friction-hydraulic draft gears now in use are characterized by a conventional friction draft gear casing having a self-contained hydraulic shock absorbing unit disposed therein for resisting inward movement of friction shoes disposed in the forward friction bore end of the casing.

This arrangement has several disadvantages in that separate rear wall structures are required for both the selfcontained hydraulic unit and the draft gear casing. As draft gears are normally of predetermined lengths so as to conform to A.A.R. standard length draft gear pockets, the volume and stroke of the hydraulic unit are therefore limited by the internal longitudinal dimension of the easing between the outermost position of the friction shoes and the inner face of the rear wall. This disadvantage is of particular importance in the so-called shorter pocket draft gears. In addition, access to the metering pin of the hydraulic unit for adjustment or replacement and access to the filling port of the hydraulic unit can be had only by removal of the unit from the gear casing which, of course, is time consuming and represents main tenance expense and inconvenience.

The present invention overcomes the aforementioned problems of draft gears having both friction and hydraulic shock absorbing components in a simple and ingenious manner. Thus, by utilizing the rear wall of a self-contained hydraulic shock absorbing unit as a portion of a removable rear wall of a draft gear casing, a hydraulic unit having a greater volume and a longer stroke may be utilized without increasing the over-all length of the draft gear. In addition, this novel arrangement provides convenient access to the metering pin and thefilling port disposed in the rear wall of the hydraulic unit.

It is therefore a primary object of the present invention to provide an improved draft gear arrangement of the type employing a self-contained hydraulic shock absorbing unit for use in railway cars.

It is another object of the present invention to provide a common rear wall structure for both a hydraulic shock absorbing unit and the casing of a draft gear within which the hydraulic unit is disposed.

It is another object of the present invention to permit facile access to the metering pin and the filling port of a hydraulic shock absorbing unit disposed within a draft gear casing.

The above and other objects of the present invention will become apparent on examination of the following specification and claims, together with the drawings, wherein:

FIGURE 1 is a plan view of a draft gear embodying the invention, taken partially in horizontal section on the line 11 of FIGURE 2;

FIGURE 2 is an eievational view thereof, taken partially in vertical section on the line 2-2 of FIGURE 1;

FIGURE 3 is an enlarged scale front end View thereof, taken partially in vertical section on the line 33 of FIGURE 1; and

FIGURE 4 is an enlarged scale rear end view of the draft gear.

Referring now to the drawings, a draft gear embodying the invention is indicated generally by the reference character it It comprises a generally cylindrical outer casing or housing 12 open at both ends and of generally rectangular shape defined by vertical side walls 14 and is and horizontal top and bottom walls 18 and 24), re spectively. The top and bottom walls 18 and 20 are characterized by undulations 21 with the crests and troughs of same extending generally parallel to the longitudinal axis of the casing 12, which undulations are spaced from opposite ends of the casing 12 and serve to aid in rigidifying same.

The casing 12 terminates at its front or forward friction end in a neck portion 22 having a hexagonallyshaped inwardly tapering friction bore 24 in which are slidingly received a vplurality of friction shoes 26. The outer surfaces of the friction shoes 26 are tapered complementary to the friction bore 24 and are adapted for sladable friction engagement therewith in a manner well known in the art. A centrally protruding wedge 30 is provided for engagement with the friction shoes 26 and serves to transmit external buff ortdraft shock forces through the friction shoes 26 to a hydraulic unit 32 which is disposed in the casing 12 inwardly of the shoes 26.

The hydraulic unit 32 is located in a chamber 34 formed within the casing 12 inwardly of the friction bore 24- and is adapted to resist inward movement of the friction shoes 26. The hydraulic unit 32 is of a type known as an air-return hydraulic unit and the novel operational and internal structural details thereof will now be described.

The hydraulic unit 32 includes an open-ended pressure cylinder 36 which is characterized by a novel rear wall 37 to be described in detail hereinafter and by a pressure tube 38 secured thereto and a ram assembly 39 telescopically mounted in the pressure cylinder 36 and which is characterized by a piston rod tube 40 and by an end cap 41 secured to the outer end thereof. The hydraulic unit 32 is disposed in the casing chamber 34 in its normal fully extended condition with the end cap 41 in engagement with the inner ends of all of the friction shoes 26 whereby the end cap serves as a follower member.

A metering pin 42 which projects axially into the presssure tube 36 from the end wall 37 thereof has one end threadedly mounted in a central through opening 12a formed in the end wall 37 in a manner such that the metering pin 32 may be readily removed from the hydraulic unit 32 from a position externally thereof, i.e. the outer face of the end wall, without otherwise dissassembling the hydraulic unit, as, for instance, to replace one metering pin with another one having different metering characteristics. As best illustrated in FIGURE 4, the metering pin 42 is provided with a hexagonal-shaped head 43 at its secured end, which head is disposed in an enlarged counter-bore or socket 44 provided in the outer face 45 of the end wall 37, whereby the hexagonal head 43 is readily engagea-ble by a standard socket wrench for assembly and disassembly of the metering pin 42 in and from the hydraulic unit 32. A piston 46 having an orifice plate 47 associated therewith is mounted on the inner end of the piston rod tube 49 and is centrally recessed to accommodate passage of the metering pin 42 therethrough. A conventional relief valve including a sleeve member 48 and a spring 2 9 is provided in the piston 46. p

A piston'like accumulator member 5h is sealingly mounted in the piston rod tube 40 for longitudinal movement relative thereto and has associated therewith an elongated guide pin 51 which is telescopically received in an axial bore 52 provided in the non-secured end of arouses the metering pin #2 to prevent canting of the accumulator member in the tube 40. A stop ring 53 mounted on the outer surface of the piston rod tube as is engageable with an annular gland member 5 5 which is mounted on the outer end of the pressure tube by suitable fastener means to determine the maximum extended condition of the hydraulic unit 32, as illustrated in the lower portion of FIGURE 2. Full closure of the hydraulic unit 32 is determined by engagement of the stop ring 553 with a beveled shoulder 55 formed on the inner surface of the pressure tube 38.

When the hydraulic unit 32 is in its normal fully extended condition, as in FIGURE 2, an annular high pressure chamber 56 defined in the pressure cylinder 3-6 by the rear wall 37, by the piston assembly 4'5 and by the metering pin 42 is filled with hydraulic fluid and a chamber 57 defined in the piston rod tube 46 by the end cap 4 1 and by the accumulator member 5% is charged under pressure with a suitable inert gas, such as nitrogen. Although the initial pressure of the gas charge in the chamber 57 may vary in different units, the gas pressure in the unit 32 disclosed in the drawings would be in the order of 200 p.s.i. The chamber 57 is charged through a conventional gas valve (not shown) which is mounted in the end cap 41 and it is noted that the gas must be not only'inert but also moisture free. The hydraulic fluid chamber 56 is fillable through a filling port 58 which is formed in the end wall 37 and which is normally losed by a suitable plug or cap 59 disposed in an enlarged counter-bore 590. provided in the outer face of the end wall 37, which plug or cap is readily accessible externally of the unit 32, iJe. at the outer face d5 of the end wall 37.

When buff or draft forces are applied to the draft gear 10, the friction shoes 26 are moved inwardly of the casing 12. As the friction shoes are in engagement with the end cap 41 of the ram assembly 3% the hydraulic unit 32 is closed as the friction shoes 26 are moved inwardly. As the piston as thereof is moved inwardly, the hydraulic fluid in the chamber 56 is metered through suitable orifices (not shown) defined by the metering pin 42 into a low pressure chamber so defined in the piston rod tube 4% between the piston 46 and the accumulator member St). As more and. more of the hydraulic fluid is metered into the chamber 60, the accumulator member St) is forced toward the end cap 41 to enlarge the chamber oil so that same is able to accommodate the hydraulic fluid metered into same from the chamber 56. However, this latter movement of the accumulator member 5t) decreases the volume of the chamber 57 and further compresses and thus increases the pressure of gas filling same. Thus, when the buff or draft forces acting on the draft gear are released, the expansion of the compressed gas in the chamber 57 serves to return the hydraulic unit 32 to its normal fully extended condition in an obvious manner whereby the friction shoes 26 are returned to their normal positions in the friction bore 24.

To prevent leakage of the hydraulic fluid from the high pressure chamber 5'6, the piston 46 is provided with an annular automotive-type cast iron sealing ring '76 and with an annular O-ring '77 spaced axially therefrom, with the sealing ring 76 being disposed nearest to the working face of the piston 46. Any high pressure fluid leakage past the sealing ring 76 is bled into the low pressure chamber 6% through a series of passages '73 formed in the piston 46, the passages '73 having open ends disposed about the periphery of the piston 46 intermediate the sealing ring 76 and the O-ring 77. The piston is also provided with an annular wear plate 79 between the sealing member '76 and the O-ring 77 for bearing purposes. In addition suitable sealing members of known types are provided for the accumulator member 50 and the mounted end of the metering pin 42.

It is noted that the closing characteristics of the draft gear llll may be varied by utilizing metering pins having different metering characteristics. For instance, it may be desirable that the resistance to closing be greatest initially after which the resistance to closing decreases gradually or that the resistance to closing be uniform through out the stroke of the hydraulic unit.

Another one of the important features of the present invention is the novel configuration of the rear wall of the pressure cylinder 36 whereby same serves both as the rear wall of the hydraulic unit 32 and as all or a portion of the rear wall of the draft gear casing. This novel arrangement permits use of a hydraulic unit having a greater volume and a longer stroke than a standard hydraulic unit disposed in a draft gear casing having a standard rear wall, without increasing the over-all len th of the draft gear. This arrangement also provides convenient access to the metering pin 43 and the filling port 53 of the hydraulic unit 32 without it being necessary to re. love the hydraulic unit from the draft gear casing.

in the form of the invention illustrated in the drawings, the hydraulic unit 32 is retained in the gear casing 12 by a locking ring 61 which co-acts with the rear wall 37 of the unit 32 in a manner such that the outer face :5 of the rear wall 37 and the outer surface 62 of the ring 61 together define a closure for the open rear end of the gear casing 112. The rear wall 37 of the hydraulic unit 32 is generally rectangular and may be described as having a rearwardly disposed stepped configuration. This stepped rear wall configuration is characterized by a first generally rectangular boss-like formation 63 which is se cured, as by welding, to the rear or inner end of the pressure tube 38 and which has four rearwardly converging tapered side walls or and by a second smaller generally rectangular boss-like formation 65 which is centered on the rear face of the boss-likeforrnation 63 and which has four rearwardly converging tapered side walls 66 and a rear face which serves as the outer face 45 of the rear wall 37 of the hydraulic unit 32. The rectangular ring-like peripheral portion of the rear face of the bosslike formation 63 disposed outwardly of the smaller bosslilie formation 65 provides a rearwardly facing four-sided shoulder or seating surface 67. As best illustrated in FlGURE 4, the vertical side leg portions of the shoulder 67 have a greater width than the horizontal upper and lower leg portions thereof.

The locking ring 61 which is generally rectangular has an outer configuration such that same is adapted to be fitted in the open rear end of the draft gear casing 12 and a stepped generally rectangular central opening 63 which is adapted to receive and mate with the stepped rear wall 37 of the hydraulic unit 32. As illustrated in the drawings, the central opening 68 in the locking ring 61 is characterized by four inwardly diverging tapered side walls 69 which are complementary to the converging side walls 66 of the second smaller boss-like formation 65, by a four-sided inwardly facing shoulder or seating surface 7% which is complementary to the rearwardly facing shoulder 67 of the rear wall 37, and by four inwardly diverging tapered side walls 71 which are complementary to the converging side walls 64 of the first larger boss-like formation 63.

To retain the locking ring 61 in the open rear end of the gear casing 22, the upper and lower edges of the locking ring at are provided with outwardly projecting peripheral flanges 73 which are engageable behind inwardly turned flanges 74 formed on the rear edges of the top and bottom walls 18 and Ztl of the draft gear casing 12. Depending upon the specific design of the draft gear casing, the ring flanges 73 and the casing flanges 74 may be continuous or, as in the embodiment illustrated in the drawings, centrally interrupted to accommodate centrally disposed inwardly extending strengthening ribs 75 which are provided in the rear portions of the top and bottom walls 18 and Ztl of the draft gear casing 12-.

In assembling the draft gear it), the wedge 3t and the friction shoes 26 are inserted into the casing 12 in a conventional manner Whereafter the hydraulic unit 32 is illserted through the open rear end of the casing until the end cap 41 engages the inner ends of the friction shoes. External pressure is then exerted by a suitable tool against the end wall 37 of the unit 32 to close same sufiiciently to permit the locking ring 61 to be inserted, in a canted position, past the casing flanges 74 into the casing 12. The external pressure is then gradually relieved to permit the hydraulic unit 32 to return to its normal fully extended condition with the stepped end wall 37 thereof seating itself in the stepped opening 68 in the locking ring 61 and with the ring flanges 73 in turn being seated against the casing flanges 74. Although the hydraulic unit 32 is well stabilized in the casing 12 by the locking ring 61, it is noted that the undulations 21 in the top and bottom casing walls 18 and 20 may aid in stabilizing the hydraulic unit 32 in a vertical direction.

It is noted that the rear wall of the hydraulic unit 32 could readily be adapted to be mounted in the open rear end of a suitably designed draft gear casing by other means, such as a bayonet-lock-type connection, for instance. The primary consideration need be only that the rear wall of the hydraulic unit also serves as the rear wall of the draft gear casing and thus not only provides ready access to the metering pin and the filling port of the unit but also permits use of a hydraulic unit having a longer stroke and a larger volume, without increasing the overall length of the draft gear, than if separate rear wall structures were required for both the hydaulic unit and the draft gear casing. Therefore, the foregoing description of one embodiment of the invention is not intended to limit the inventive concept to that illustrated, but instead the limitations of the described invention are set forth in the accompanying claims.

What is claimed as new is:

1. A draft gear comprising, in combination, a draft gear casing open at both its front and rear ends and having a friction bore at its front end, a series of friction shoes disposed in said friction bore and having a wedge associated therewith for actuating same, a normally fully extended hydraulic shock absorbing unit disposed in said casing inwardly of Said friction shoes and characterized by a pressure cylinder one end of which is closed by an end Wall having a stepped configuration on its outer face, said cylinder having a movable ram projecting from the opposite end thereof, said hydraulic unit being disposed in said casing with said cylinder end wall disposed in said open rear end of said casing and with the end of said ram in engagement with the inner ends of said friction shoes, and a locking ring disposed in encircling relationship about said cylinder end wall and having an inner peripheral stepped configuration complementary to said stepped configuration of said cylinder end wall for receiving same therein and an outer peripheral configuration engageable with flange means provided on said open rear end of said casing, whereby said locking ring and said cylinder end wall of said hydraulic unit define a removable end Wall for said casing.

2. A draft gear comprising, in combination, a draft gear casing open at both its front and rear ends and having a friction bore at its front end, a series of friction shoes disposed in said friction bore and having a wedge associated therewith for actuating same, a normally fully extended hydraulic shock absorbing unit disposed in said casing and characterized by a pressure cylinder having one end closed by an end wall and a movable ram projecting from its opposite end, said hydraulic unit being disposed in said casing with said cylinder end wall disposed in said open rear end of said casing and with the end of said ram in engagement with the inner ends of said friction shoes whereby to oppose inward movement thereof, said cylinder end wall having a stepped configuration on its outer face and said rear end of said casing being provided with inwardly turned flanges, a locking ring for removably mounting said end wall of said cylinder in said open rear end of said casing in a manner such that said end wall of said cylinder and said locking ring define a rear wall for said casing, said locking ring being disposed in encircling relationship to said cylinder end wall and having a stepped inner peripheral configuration complementary to said stepped configuration of said cylinder end wall and outer peripheralflanges engageable with said casing flanges, and a through opening formed in said cylinder end wall and serving as a hydraulic fluid filling port for said hydraulic unit, said filling port being provided with a removable closure member, said arrangement providing ready access to said filling port closure from externally of said draft gear casing.

3. A draft gear comprising, in combination, a generally rectangular draft gear casing having top, bottom and side walls, said casing being open at both its front and rear ends and having a friction bore at its front end, a series of friction shoes disposed in said friction bore and having a wedge associated therewith for actuating same, a normally fully extended hydraulic shock absorbing unit disposed in said casing and characterized by a pressure cylinder having one end closed by an end wall and a movable ram projecting from its opposite end, said hydraulic unit being disposed in said casing with said cylinder end wall disposed in said open rear end of said casing and with the end of said ram in engagement with the inner ends of said friction shoes whereby to oppose inward movement thereof, said cylinder end wall having an outwardly diverging stepped configuration on its outer face and the rear edges of said top and bottom walls of said casing being provided with inwardly turned flanges, a generally rectangular locking ring for removably mounting said end wall of said cylinder in said open rear end of said casing in a manner such that said end wall of said cylinder and said locking ring define a rear wall for said casing, said locking ring being disposed in encircling relations-hip to said cylinder end wall and having both an inwardly diverging stepped inner peripheral configuration complementary to said stepped configuration of said cylinder end wall and outer peripheral flanges engageable with said flanges on said top and bottom casing walls, a pair of through openings formed in said cylinder end Wall with one of said openings serving as a hydraulic fluid filling port for said hydraulic unit, said filling port being provided with a removable closure member, and a metering pin extending into said pressure cylinder and having one end removably mounted in said other opening in said cylinder end wall, said arrangement providing ready access to said metering pin and said filling port closure from externally of said draft gear casing.

4. In a draft gear characterized by a draft gear casing open at both ends and having a friction bore at its front end, and by a series of friction shoes disposed in said friction bore and having a wedge associated therewith for actuating same, a hydraulic shock absorbing unit disposed in said draft gear casing for resisting inward movement of said friction shoes and comprising, a pressure cylinder having its rear end closed by a rear end wall which is disposed in the open rear end of said draft gear casing and which serves as a rear end wall for said casing, means for removably mounting said cylinder end wall in said open rear end of said casing, a ram assembly telescopically mounted in the front end of said pressure cylinder and being characterized by a piston rod tube having a piston mounted on its rear end and an end cap mounted on its front end for engagement with the inner ends of said friction shoes, a metering pin having one end mounted in the center of said rear end wall and projecting forwardly into said pressure cylinder and through a central opening formed in said piston, said pressure cylinder being filled with hydraulic fluid and said metering pin and said piston opening defining orifice means between the opposite faces of said piston, a piston-like accumulator member floatingly mounted in said piston tube and biased toward said piston by a pressurized charge of gas in the front portion of said piston rod tube, and a guide pin mounted in the center of the rear face of said accumulator member and projecting rearwardly therefrom into telescopic relationship in an axial bore formed in the forwardly projecting end of said metering pin whereby to prevent canting of said accumulator member in said piston rod tube during relative movement therebetween.

5. A draft gear as recited in claim 4 wherein a high pressure chamber is defined in said pressure cylinder between the rear face of said piston and said rear end wall and a low pressure chamber is defined in said piston rod tube between the front face of said piston and the rear face of said accumulator member, wherein a metallic sealing ring is provided about the peripheral surface of said piston adjacent the rear face thereof, wherein an O-ring is provided about the peripheral surface of said piston in forwardly spaced axial relationship to said metallic sealing ring, and wherein passage means extend from the portion of the peripheral surface of said piston disposed between said metallic sealing ring and said O-ring through said piston into said low pressure chamber for bleeding any high pressure hydraulic fiuid leakage past said metallic sealing ring into said lower pressure chamber.

6. In a draft gear characterized by a draft gear casing open at both ends and having a friction bore at its front end, and by a series of friction shoes disposed in said friction bore and having a wedge associated therewith for actuating same, a hydraulic shock absorbing unit disposed in said draft gear casing for resisting inward movement of said friction shoes and comprising, a pressure cylinder having its rear end closed by a rear end wall which is disposed in the open rear end of said draft gear casing and which serves as a rear end wall for said casing, a locking ring engageable with both said cylinder rear end wall and said casing open rear end for removably mounting said cylinder end wall in said open rear end of said casing, a ram assembly telescopically mounted in the front end of said pressure cylinder and being characterized by a piston rod tube having a piston mounted on its rear end and an end cap mounted on its front end for engagement with the inner ends of said friction shoes, a metering pin having one end mounted in the center of said rear nd Wall and projecting forwardly into said pressure cylinder and through a central opening formed in said piston, sa d metering pin having an axial bore formed in its forward end, said pressure cylinder being filled with hydraulic fluid and said metering pin and said piston opening defining orifice means between the opposite faces of said piston, a piston-like accumulator member floatingly mounted in said piston tube and biased toward said piston by a pressurized charge of gas in the forward portion of said piston rod tube, and a guide pin mounted in the center of the rear face of said accumulator member and projecting rearwardly therefrom into telescopic relationship in said axial bore for-med in said forward end of said metering pin whereby to prevent canting of said accumulator member in said piston rod tube during relative movement therebetween.

References Jilted by the Examiner UNITED STATES PATENTS 1,909,768 5/33 Jones.

2,808,945 10/57 Danielson 213-22 2,994,442 8/61 Frederick 2=13-43 FOREIGN PATENTS 296,712 7/29 Great Britain.

EUGENE G. BOTZ, Primary Examiner.

0 LEO QUACKENBUSH, Examiner. 

1. A DRAFT GEAR COMPRISING, IN COMBINATION, A DRAFT GEAR CASING OPEN AT BOTH ITS FRONT AND REAR ENDS AND HAVING A FRICTION BORE AFT ITS FRONT END, A SERIES OF FRICTION SHOES DISPOSED IN SAID FRICTION BORE AND HAVING A WEDGE ASSOCIATED THEREWITH FOR ACTUATING SAME, A NORMALLY FULLY EXTENDED HYDRAULIC SHOCK ABSORBING UNIT DISPOSED IN SAID CASING INWARDLY OF SAID FRICTION SHOES AND CHARACTERIZED BY A PRESSURE CYLINDER ONE END OF WHICH IS CLOSED BY AN END WALL HAVING A STEPPED CONFIGURATION ON ITS OUTER FACE, SAID CYLINDER HAVING A MOVABLE RAM PROJECTING FROM THE OPPOSITE END THEREOF, SAID HYDRAULIC UNIT BEING DISPOSED IN SAID CASING WITH SAID CYLINDER END WALL DISPOSED IN SAID OPEN REAR END OF SAID CASING AND WITH END OF SAID RAM IN ENGAEMENT WITH THE INNER ENDS OF SAID FRICTION SHOES, AND A LOCKING RING DISPOSED IN ENCIRCLING RELATIONSHIP ABOUT SAID CYLINDER END WALL AND HAVING AN INNER PERIPHERAL STEPPED CONFIGURATION COMPLEMENTARY TO SAID STEPPED CONFIGURATION OF SAID CYLINDER END WALL FOR RECEIVING SAME THEREIN AND AN OUTER PERIPHERAL CONFIGURATION ENGAGEABLE WITH FLANGE MEANS PROVIDED ON SAID OPEN REAR END OF SAID CASING, WHEREBY SAID LOCKING RING AND SAID CYLINDER WALL OF SAID HYDRAULIC UNIT DEFINE A REMOVABLE END WALL FOR SAID CASING. 